Will the control rods ultimately absorb enough neutrons to completelyo stop the heat generating in the reactor vessel or will pumped water be required to remove residual heat even in a stable or cool mode due to random neutron exchange between cool fuel rods?

A: Adrian Heymer

First, I would like to express my concern for all those affected by the earthquake. Our thoughts and prayers go out to the people of Japan and the workers at the Fukushima Daiichi plant and their families.

In response to your specific question ... eventually the heat remaining in the fuel will reach a stage that will enable it to be removed or permanently encased. That likely won't for a number of years. Until then, the fuel will have to be cooled with water.

How much radiation can destroy our civilization? How can we prevent the radiation effects?

A: Adrian Heymer

Radiation exists in nature, and we are all exposed to it every day. Scientists know that certain levels of radiation are not harmful. However, higher levels of radiation over short periods of time can be very harmful.

It seems that daily the situation worsens, today we read a fuel pond fire is now spreading radiation. Where do you see things heading, obviously each plant is a unique situation, but could you focus on one plant in particular and tell us things like: what's the ETA to contain a meltdown? is "meltdown" still the right term? what's the best case scenario right now for a resolution?

A: Adrian Heymer

First, the cause of the fire reported at Unit 4 is not linked to the fuel in the pool. The fire was associated with equipment in the vicinity of the fuel pool.

Tokyo Electric Power is working to engineer a system to add water to the fuel pool.

I suggest the word "meltdown" is too strong. "Damaged" is a more accurate word if the fuel in the pool has been affected.

The Onagawa nuclear plant is much closer to the earthquake and tsunami zone but appears to have shut down safely while Fukushima I has not. Can you explain the differences in what happened and is happening at the two nuclear locations?

A: Adrian Heymer

All we know at this point is that the Onagawa plant has been shut down safely and does not appear to have been severely affected by the tsunami or the earthquake.

The workers at the Fukushima plant have attempted to manage and mitigate the effects of an extreme natural disaster that has completely destroyed the towns and countryside surrounding the plant and their homes. Yet they continue to work in highly adverse conditions. The actions taken by Tokyo Electric Power and the government of Japan to evacuate 200,000 people in an orderly manner -- with devastation of transporation and communications systems -- is extremely commendable.

No doubt when the situation has stablilized, Japanese and international nuclear experts will review the actions taken and incorporate lessons learned from this event.

Hi - What are the potential impacts of the meltdowns in Japan on California (West coast) and Hawaii? Please assess it as you see the situation now (reactors 1, 2, 3 in partial meltdown, fire in #4, temps rising in #5 and #6) and if a worst-case scenario were to play out (full meltdown with release of all plutonium and other radioactive material). Should public policy makers be taking steps to safeguard the public against such a scenario? What can concerned citizens do to prepare? Thanks - Dan (age 38), Nadia (age 36), Taybi (age 6 months)

A: Adrian Heymer

Dan, Nadia and Taybi:

At this stage, we don't see any impact on the West Coast or Hawaii from the earthquake and the effects on the Fukushima plant.

In a worst case scenario with the damaged Fukushima Daiicchi reactors going into partial (if not there already) or complete meltdown, what will be the overall impact not only locally but internationally on an environmental and human life cost basis?

A: Adrian Heymer

You may recall that the worst commercial nuclear plant accident in the United States, the Three Mile Island accident in 1979, involved a partial melting of the reactor core. There were no fatalities or injuries as a result of the accident, though it caused considerable stress.

Why is the situation playing out over many days versus hours or even minutes?

A: Adrian Heymer

The heat from nuclear reaction takes a long time to dissipate. As a result, it takes time to return the plant to a stable condition. Once in a stable condition, action will be taken to decommission those facilities where fuel damage has occurred. This will take many years.

I am a college student who was in the final stages of making plans to study abroad in Japan when the tsunami hit. I understand that cleaning up the damages from the tsunami will be daunting in and of itself and will likely delay travel plans for the next few months, but how long will travel plans be delayed if the nuclear power plant does not stabilize? Is there a recommendation for how long travelers should avoid the area if a serious nuclear meltdown does occur? I have many Japanese friends who are also wondering when they will be able to go home if the situation in Japan does become any worse. Any information on the subject would be helpful. Thank you.

A: Adrian Heymer

We share your concerns. Unfortunately, we are unable to provide accurate projections or advice on your travel plans.

The extensive failure of emergency safety systems at the Japanese reactors raises the question, "why do we in the US subsidize the nuclear industry by putting a ceiling on the maximum liability that a nuclear power generation company faces in the event of a catastrophe?" Wouldn't the industry take steps to increase safety and reduce fraud if it was required to fully insurance against the damage it might cause?

A: Adrian Heymer

To clarify ... the safety sytems worked properly at the Fukushima plant following the earthquake until the tsunami hit the plant. The tsunami destroyed the electrical power systems that supported the safety systems. The alternative safety systems continued to work until the thermal conditions caused those alternative safety systems to fail. The extensive devastation within and external to the plant caused by the tsunami hampered restoration efforts.

In the United States, the power companies are required by law to purchase liability insurance (via the Price-Anderson Act), which is pooled should an accident occur and whose exceeds $10-12 billion.

Over the past 20 years the safety at nuclear power plants in the U.S. has been increased at least five-fold.

US. nuclearpower plants along with those of other nations have developed procedures and protocols for dealing with severe accidents of the type seen in Japan.

After the explosiion at the #2 reactor, the Japanese government and IAEA have said that there is likely a crack in the containment vessel. News reports, however, have left me unclear on whether they are talking about the inner reactor vessel or the primary containment (with the drywell & wellwell). Can you clairify?
Also, if the primary containment is breeched, does the secondary containment building have more flooring that would stop a melted core?

A: Adrian Heymer

At this stage it is unclear whether the containment structure has been damaged or the extent of any damage. Circumstantial evidence appears to indicate that the containment structure may have been damaged, yet I have not seen confirmation of this by the Japanese governement or Tokyo Electric Power.

Adrian Heymer is the Executive Director, Strategic Programs, at the Nuclear Energy Institute (NEI) in Washington, DC, USA. He is responsible for integrating the commercial nuclear industry’s strategic programs and directing NEI’s activities in support of the nuclear industry’s suppliers. Until recently, he was the senior director responsible for coordinating the nuclear industry’s generic activities on new nuclear plants. Other responsibilities at NEI have included electricity deregulation, plant performance improvement, regulatory reform, and quality programs.
Prior to joining NEI he worked in support of Nebraska Public Power District’s Cooper Nuclear Station, Nebraska, as an engineer and manager; at Lloyds Register on technical certifications, inspections and repairs of industrial and marine equipment, facilities and ships; and served 16 years in the Royal Navy.